It is commonplace in both industrial and commercial applications that employees are called upon to move bulky and heavy objects from one location to another. Such tasks present a risk of injury not just to the employees directly involved in the relocation task, but to other employees in the vicinity of the involved employees. In addition, moving bulky objects in the workplace requires dedication of man-power and time resources, which add operating costs to businesses. Tires are an example of a bulky object that poses an injury risk to the employee when being moved from one place to another. The average passenger car tire weighs between 25 and 50 pounds. The average pickup truck tire weighs between 50 and 75 pounds. A tire for a tractor trailer can weigh over 100 pounds.
Tire manufacturers, large-volume tire sellers and motor vehicle manufacturers are examples of businesses whose workers are engaged in extensive lifting of tires. These businesses rely upon specialty devices called tire manipulators to move tires from one location to another. This is especially true for tire manufacturers whose employees must lift and position an individual green tire (the uncured tire product produced by a tire building machine) and cured tires as part of the manufacturing process.
One form of tire manipulator known in the prior art is the pneumatically activated tire manipulator that is suspended from a jib crane or bridge crane. The manipulator is suspended from a trolley that may travel horizontally on an overhead rail on the crane. These suspended manipulators employ pneumatic or electric powered lifting systems to allow operators to raise and lower a held heavy object like a tire. The manipulator has handles held by the operator and the manipulator acts as an extension of the operator's hands. The operator transfers the tire from one position to another by depressing thumb levers located on the operator handles to attach and release the tire and to raise and lower the manipulator in conjunction with the operator's movements.
FIGS. 1 and 2 depict a prior art tire manipulator 1. As shown in these figures, prior art tire manipulator 1 comprises a pair of gripper shoes 2 slidably mounted upon rail 3. In the typical arrangement, tire manipulator 1 would be suspended from a jib crane or bridge crane and pneumatically activated. Gripper shoes 2 have an arcuate perimeter surface 4 that has a radial curvature adapted to complementarily engage the inner radial surface of a tire. Gripper shoes 2 move radially inwardly and outwardly on rail 3.
In use, a user would hold handles 5 situated outwardly on handlebar 6. While holding onto the handles 5 the user can move manipulator 1 horizontally by manually pushing/pulling on handles 5. Raise and lower motions are effected by depressing thumb levers 8 on control panel 7 located on operator handle 5. The inward and outward movement of gripper shoes 2 on rail 3 is likewise controlled by the user via thumb levers 8 on control panel 7 on handles 5. To relocate a tire, gripper shoes 2 would be brought to their inboard position on rail 3, manipulator 1 would be positioned vertically over the tire and manipulator 1 would be lowered such that shoes 2 would be inserted into the cavity of the tire. Once fully inserted into the cavity, the user would cause the outward movement of shoes 2 on rail 3 until the shoes securely pressed against the inner radial surface of the tire (a/k/a the tire's bead). Once that pressure contact is achieved, the user could then initiate lifting movement to the manipulator through levers 8 on panel 7 and thereby lift and reposition the tire. Once repositioned, the user would bring shoes 2 inboard, thereby releasing the tire from the manipulator.
There are several features of the prior art tire manipulator that can be improved. In one regard, it is a common task in certain tire handling jobs to pick a tire from a conveyor height of 36 inches and place the tire on a cart. When stacking tires on a cart, the operator manipulating the tire may need to position the tire at a stack height ranging from 12 inches to 72 inches. Because of the design of the prior art tire manipulator, for an operator to position a tire throughout this height range, the handles need to effectively travel up and down to these same elevations. Thus, with the prior art tire manipulator, the fixed position handles do not allow an operator to comfortably and effectively use and control the manipulator tool. There is thus a need in the art for a tire manipulator that is more easily and comfortably usable.